Contractors Face a ‘Perfect Storm’ in Wastewater Treatment Works Projects
Posted on by Simon Cottingham
A look at some of the issues faced by clients and contractors in wastewater treatment works projects, and why higher levels of technical support from pipeline suppliers are crucial, by Simon Cottingham, Major Projects Director of Saint-Gobain PAM UK, the country’s premier supplier of ductile iron water and sewer pipelines.
Watch the video on YouTube for more info on the project.
Extensions or upgrades to wastewater treatment works by definition are located on the site of existing works. These sites have often been built on, extended or renovated over many decades. All of the challenges a contractor might encounter on a multi kilometre pipeline are condensed within the boundaries of the works and typically over 50m – 100m pipe runs. Contractors find themselves dealing with a ‘perfect storm’ of existing services and buildings, pipelines required above ground on plinths or at extreme depth, contaminated and aggressive soil as well as changes to design as work progresses and unforeseen challenges present themselves. All of this means a far higher level of day-to-day technical support is required from pipeline suppliers than would normally be required. This support, if sought at the early stages of design, can head off issues before they become major problems.
Pipe runs tend to be relatively short and navigate around the services and existing buildings typically found at wastewater treatment sites. Socket spigot systems are ideal for these applications because they offer the flexibility to cut on site to required lengths to adjust the position of fittings and to accommodate design changes.
Most designers specify concrete blocks to provide thrust restraint for socket spigot pipelines. As the pipe diameter increases so does the size and cost of concrete thrust blocks, and this can become a deterrent to specifying socket spigot systems. Occasionally, flange pipe and fittings are specified as a way of negating the need for thrust blocks but the lack of flexibility of a flange joint in buried applications will almost certainly result in premature failure. Boltless mechanical anchorage systems such as our Universal and PAMLOCK anchored joints are flexible, simple and quick to install and are a cost-effective alternative to concrete thrust blocks. Since they do not require external bolts to lock the system together there is no requirement for post-installation wrapping to protect the integrity of the bolts. On a recent project a contractor installing a 1200mm diameter Universal anchorage system took on average 15 minutes to complete the installation of each joint, which is 75% faster than the typical installation time of a traditional bolted anchor system.
There is a further common misconception that anchorage is required at every joint. This is rarely the case. Using our Pipespec anchorage calculation tool our technical team can consider all of the parameters relevant to minimise the number of joints requiring anchorage. In many cases water and wastewater is not being transported at high pressures within the confines of a treatment works and the mechanical anchorage required can be minimal. The savings in design and construction costs can be significant as well as negating the disruption to adjacent services and buildings caused when trying to position a large concrete thrust block.
Often, treatment works are built on brownfield sites with relatively aggressive ground conditions. This can be a major issue for contractors and clients requiring assurance of long-term system integrity. The implications for not applying the appropriate level of corrosion protection is unlikely to have an immediate impact on the client, but can result in an expensive and highly disruptive system failure at some point in the future. At Saint-Gobain PAM UK we offer soil surveys and ground investigation reports to enable us to provide bespoke external pipe corrosion protection systems for even the most aggressive ground conditions. Corrosion protection can be localised to the soil conditions at each pipe and any additional protection limited to areas of need rather than across the entire pipeline. Once again, early involvement of our technical team allows decisions to be made on the most appropriate level of corrosion protection to minimise cost whilst providing assurance of long-term pipeline performance.
For further information on the range of ductile iron pipes that are ideal for wastewater treatment works including the Integral range, barrier coatings, Universal and PAMLOCK boltless mechanical anchorage systems, valves, couplings, adaptors, dismantling joints visit http://www.saint-gobain-pam.co.uk.